Over the past few decades the manufacture and packaging of semiconductor components has become one of the largest industries in the world. Microcircuitry and large scale integrated circuitry have become the standard information processing and algorithm enabling devices in a wide variety of technological fields. Accordingly, the demand for such devices as well as the demand for improved quality of such devices has grown astromically.
One feature of semiconductor devices which has been the subject of much research and development is the packaging of the components themselves. It is desirable to place the chip or integrated circuit in a carrier or a package. The carrier or package protects the chip and also provides a mechanism by which the chip may be connected by larger conductive elements known as "leads" to other components. The packages and leads are in a wide variety of forms but all are designed with the idea of placing the chip carrier in juxtaposition with a circuit board or other component and causing the leads to contact the specific portions on the juxtaposed element. This provides an electrical path from the component to the chip.
A step which is necessary in preparing the chip package for use is to wave solder the leads. The solder utilized operates both as a binding element and as a conductive element. The solder is applied in a large scale to chips with the application of substantial heat such that the solder is in liquid form when it impacts the carriers and is then cooled into position.
One of the most efficient manners of applying solder is by use of what is known as a wave solder machine. This sort of device is adapted for use in applying solder essentially simultaneously to a large number of components. In this machine the components are carried through a zone, wherein wave solder is applied, by a conveyer mechanism. The device which is utilized to hold the individual packages during the wave solder process is referred to in the industry as a "pallet". These pallets have come in various different designs.
The most commonly used traditional pallet has been a device which is elongated and onto which individual chips can be slid serially into tracks specifically designed for the type of package involved. These devices typically look to be wire structures. Disadvantages which have been found with the conventional pallets are that they provide no protection for the reverse sides of the packages, they allow the packages to abut against one another and thus give rise to potential damage, and they need to be custom designed for each size of package to be utilized. Furthermore, this sort of structure does not operate well with chip carriers having leads which do not extend beyond the carriers themselves. Flat packages are difficult to both restrain and to make the appropriate surfaces available for soldering in a conventional type pallet.
One other type of pallet which has been subject of a U.S. Patent is described in U.S. Pat. No. 4,700.935, issued Oct. 20, 1987 to R. T. Winslow et al. This pallet or wave soldering fixture is adapted specifically to correct the type of problems of flat packages and other packages which do not adapt well to the conventional wave solder pallets. The Winslow device allows the chip packages to be loaded separately and held in place by a unitary gate mechanism in a carrier portion specifically designed to receive the packages. Each of the fixtures disclosed in Winslow is adapted for receiving packages of a specific size and shape.
Despite the substantial advances which have been made in pallet construction technology there remains great room for improvement. The chip packaging industry continues to create new designs and to expect higher degrees of precision at each stage of the process. Accordingly, it is desirable to create improved methods of carrying the chip packages through the wave solder machines which can accommodate a wider variety of packages and can provide increased protection for the packages during operation, while retaining excellent exposure of the package to the wave solder with minimum exposure of the pallet material, and with excellent precision as to positioning.